A Brilliant View Into Aerodynamics

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There’s probably nothing more underestimated in a car’s development and performance than actual aerodynamics. What was born as nothing more than a black art has slowly and very successfully turned into an ever-evolving technology that has the potential to improve pretty much every single aspect’s of a car’s capabilities, not to mention make the difference between winning or losing a race in a lot of forms of motorsports. However, successfully understanding and harnessing this interaction between a car and the airflow that surrounds it at any given speed is probably one of the most misunderstood modern-day sciences, explaining why many manufacturers have made huge investments in wind tunnels and super computers to virtually process an outstanding amount of data. Varying opinions and assumptions, not to mention embellished figures, there to serve as marketing tools rather than anything else, have all contributed into making aero quite confusing. It’s lucky then that I had a chance to sit down with the man of the moment when it comes to aerodynamics and its fast adoption in the world of Time Attack, Andrew Brilliant.

Andrew has so much passion for the work that he does, not only academically sculpting his path through this rather interesting career choice but on the side putting his theories to the test in a few of his very own projects. Through a mix of knowledge and careful R&D – not to mention good old trial and error – he has brought a very important and often overlooked variable into the grip world. In next to no time he has become the go-to guy if you want to make your already powerful and fast car substantially faster. He is behind the most successful cars in the Time Attack world, and thankfully has agreed to answer some questions in an attempt to make some sense of it all. Prepare to throw everything you thought you knew about aerodynamics out of the window and let your theories really be challenged.

SH:So first of all Andrew, thanks for taking some time to answer some questions. First up, just to get into the flow of things, what is it that got you interested in aerodynamics in the first place?

AB: Firstly, thank you for having me and it’s my pleasure. Some years ago, I was studying in university and I was a gear head, I was really into racing. You know how they ask you what you love and that’s supposed to tell you what you should do? So I guess that meant I should do racing and I needed to study mechanical engineering. That’s funny looking back though: I think up until just maybe 5 years ago that’s how it was thought of in the US – that aero was only for airplanes! Fluids was my favorite though. I started driving and racing in land speed events. They were really cheap to run and a lot of fun. I kept at it and learned a lot from the salt dogs, studying how the dust laid on the car, high speed photos, following big rigs in the rain, anything we could get our hands on without money for sensors and wind tunnel testing.

I started playing with Computational Fluid Dynamics (CFD) but didn’t have enough computing power to do anything significant. I started learning a lot from scale models in the bathtub, in front of fans, whatever I could think of. I was working for various amateur level racing teams and sometimes I would get chances to apply what I learned. SCCA and those kind of organizations in the States have rules against aero but if you understand aero you could see they were basically wide open… so we started winning. I remember being totally blown away by how a tiny change could take us up five positions in qualifying. I began to realize the power of what we were doing. One thing led to another and I ended up being picked by my first pro team in American Le Mans. Things grew a step at a time like that.

SH:That’s awesome, you really evolved through it all.Tell us a bit about your Mitsubishi Eclipse project. Was it always your intent to push things that far? And also what did you learn from it?

AB: The Eclipse is really what started everything and it was the key. I’m trying to compress 13 years into a brief response. I didn’t know anything about cars when I started on it. Later on, some of the work I did on it got me noticed in professional circles. It wasn’t a car that was built overnight; it was done a little bit each year for 13 years. It was my daily driver for the first three years and I have a lot of memories cruising it around until it got too crazy. I learned a lot about aero on that car. As an engineer I was never one for being all theoretical. If it cannot be readily applied, or there are too many problems, it’s useless, or worse, it’s a waste of resources.

I modelled most of my prototype concepts on that car and learned which theories can be applied cost effectively.

Believe it or not, things have trickled up from that car onto GT cars and of course to cars like Nemo and Scorch racing in Time Attack. Really, I learned how to develop a car from the ground up which is something you don’t get in pro racing. Especially developing something with that kind of downforce is normally done by manufacturers, not at the team level.

So there is a knowledge gap there. I learned how aero and chassis work together and how to set a car up and tune it track to track. Even more than that though, I think I learned about managing a team (the hard way) and what a monumental challenge that is. I’m still not any good at it, but I learned a whole lot and I’ve now got a new respect for the team managers.

I guess you want to know more on the aerodynamics side though? For that, I would say that I learned the most about pitch sensitivity, which is the way the aero changes when the car brakes and accelerates. Every car suffers from that, but that car even more so by being front-wheel drive and just having a lot of downforce. The goal was to achieve a near zero pitch sensitivity without much hit in peak forces. That is still ongoing but very close to its goals. The last time I drove it on the street…

… this is probably something I should not talk about! We just finished installing the first generation of the body and I took the car for a test drive. There was an off-ramp near my house: a 180 degree sweeper rated at 45mph. I thought I’d see how fast it could go there.

I did it at 120mph and it didn’t feel difficult! I think I parked the car and flipped out.

It could slalom the dots between freeway lanes and sunk down 25mm when you got up to speed. I knew I was going to get into a heap of trouble though, so I took the license plate off and that was the end of the street car days.

SH:I’m sure you get a lot of questions from people querying you about the finer points of aero design. Let’s pretend I’m a diligent enthusiast: well-prepared as I’ve proudly invested in a copy of Competition Aerodynamics – A Practical Handbook, so I assume I know all there is to know about Cd, airflow and downforce. What would you say to me if I told you that it’s easy to make a car improve its aero load around corners, just add a splitter, some canards and a large bi-plane wing and I will be on my way to faster times. Plus the bigger each of these components are, the better. Comments?

AB: I would say the most misunderstood thing about aero for the general public is that people think there is one perfect shape and we [aerodynamicists] know what it is, so they are always asking you to tell them. The truth is, there is no good solution that isn’t a custom one and even defining what is better is circumstantial. We call the details of the car the packaging and packaging is the name of our game. Arranging things to make the aero work and making the aero work with the way things are arranged. Bigger is not always better and testing is king. I think that the real questions to ask are: why did this work, why didn’t this work like I expected and what is the next thing to try?

Let me explain about that a bit more. Initially aerodynamics seems so intuitive. If you put a flat plate inclined to the wind it makes downforce. So all you need to know is what angle makes the most downforce, the least drag or whatever. So in that sense a diffuser is intuitive. But it gets complicated when you have a suspension part protruding into the air stream, a dirty rolling tire wake, air coming from whatever of a million things in the front of the car or the car in front of you, hot air off the exhaust and a five mph cross wind at two degrees of yaw or half a degree pitch under braking. All this stuff interacts. It’s about how all the parts work together as a system so unless you understand all the parts you can get it all wrong.

The same design will not work on another car and that constantly surprises you. Everything in front has a huge effect on the rear and vice versa. What it boils down to is that aero is simple until you get to the interactions, then it’s far too complex for a human brain to work out. That is why people spend tens of millions on supercomputers and wind tunnels. Your tools are everything; you need repeatable and accurate test methods. Your processes are critical because the tools are worthless if you are not religious about how you use them. After that you need to apply what you have learned to guide testing. That’s the core of what we do really; there are infinite shapes to test, but you need to get the right one, or at least get it more right before the other teams. It boils down to experience, discipline and your gut.

The metric for my performance is the number of iterations to goal within, at whatever accuracy you can manufacture. There are always more ideas and more tests you can do. If you improve your manufacturing techniques, the optimum goes up to another level. That’s why you see motorsports getting faster every year, even inside of rules that don’t change much and try to limit aerodynamics. With that said, there are things which you will know work most of the time but they are very few and you can never apply them the same on more than one car.

SH:Well since we are here we have to talk about Nemo. Would you say that is the perfect example of what a ground-up aero package can achieve? It kind of almost ridiculed the competition and forced a change in the WTAC regulations.

AB: We came into the event without even having a baseline for the car so we did not expect the result. I wouldn’t say its perfect. When you finish a car design, if you have a good team like we did, you can put all your best ideas into it. Then you start to run the car and new ideas start flowing. It’s been three years since the car was designed and all those technologies have newer versions that perform much better. Technology in the sport took a big jump at that moment, but people can and already are rising to the new challenge.

The rules have shifted and hurt us by way of a +110kg minimum weight, which is huge. Basically there was a small group of one or two teams that were vocal in saying it would be a one-car race. The rule makers decide for their reasons though, so you respect that and do your job. As a friend of mine always says “Get me a drawing board and some caffeine!” Maybe you lose sight after that, but if you have the attitude that you can overcome, I think you will, it’s just a matter of when.

SH:No matter how efficient a design you sculpt, at the end of the day the main job comes down to suspension and tires. With the sorts of loads you are generating on the more extreme cars these components must be under some serious strain, right?

AB: The car has a good amount of travel and we bottomed out the suspension early on the straight which to give some idea takes over 3 tonnes on the springs to do. I was worried about tires but Hankook had an engineer on site for me to work out a solution. We are struggling with wheel bearing loads and also the wheels themselves are way outside of their design parameters, especially with the lap count. RAYS is working on some trick stuff for the car now. Last year the engine was set at a very conservative ~450hp, so with the higher top speeds expected and new tire regulations it is an even more serious concern.

SH:What sort of things did you come up with to overcome the the weight penalty?

AB: We used a couple of strategies and some weight came from rules compliance. The rest of it will be taken up by my new favorite part, which is a tuned mass damper. Maybe the easiest way to explain it is to imagine the car is a weight and you put the weight on top of a spring, which is like the suspension. Push down on the weight and let go: the weight will bounce up and down. Now you put another identical spring on top of that and an identical weight on top of the second spring. The first weight will not bounce as much any more. It lets you keep the tire loads more stable as the suspension moves and you get more grip.

SH:One project you’ve been involved in is one we have followed for years here at Speedhunters, and that is of course Under Suzuki and his inspiring road to that Tsukuba record. How has that car progressed through the years and how much more scope is there to go even faster for everyone’s favorite Time Attacker?

AB: Suzuki-san has taken a very incremental approach to his car build: little steps at a time over a lot of events along the way. His pace of development can be admired as can his level of knowledge. Going from 55 seconds to 52 seconds in a bit over two years. He’s right on pace to the fastest-developing teams ever and you can be sure they were spending more money.

He has primarily focused on building out aerodynamics and I have been designing for him. I probably cannot talk much about what he’s up to now.

SH.Interaction of air and flow around a car is extremely complex. But it’s not only the surface and underside of a car that come into play, how about the air that enters through a front air dam for example, or a wheel arch?

AB: Aerodynamics are just a system to manipulate air, your goal is to create low and high pressure regions on your working surfaces. So if you plan on maximizing the performance, you cannot neglect a single surface on the vehicle. Everything has to be helping and air goes from one place…

… to the next. Everything is an interaction and it all has to tie together in a positive way. Suzuki-san has used I think two events just this year on testing iterations of wheelhouse stuff; you probably saw him building temporary parts just like you do in the wind tunnel, except he is going by feel, lap time and top speed because that is his budget. You gotta admire that kind of passion!

SH.You have been working on a pretty special project with one of your customers from Norway lately. It’s a car that we will all be seeing at this year’s Gatebil event in Rudskogen. What can you tell us about this rather unique Subaru BRZ project?

AB: Yes, this car is being built by a long-time customer of mine, Lars Harlem. It is meant to compete in a local GT series in Norway and Gatebil. As far as the aero, it was an all-CFD project with a design target of similar downforce and less drag than a Super GT GT500 car and right up there with a current early season Formula 1 car. He just took delivery of the base chassis and construction work has begun.

SH. And finally, how do you hope to see the mathematical art of aerodynamics develop over the next decade and beyond?

If you look at a photo of a 2002 Formula 1 car now and compare that to say a 2007 car, you can see that a huge leap happened there aerodynamically. Same with Super GT. There was an explosion in aerodynamic testing and huge growth in CFD techniques. F1 is where most of the money in vehicle aerodynamics is spent and they will push into wherever the unintended consequences of the rules lets them. There is a big shuffle now in Super GT with the DTM rules and people are concentrating on that.

I think in the long term, it’s now realized that aerodynamics are the place where the most performance is and the more you place rules on it, the more you realize that it’s unstoppable. Even in the spec body stuff like IndyCar or Nascar it’s still the dominant factor. By placing so many rules on it they slowed down the progression as intended, but as long as the gap exists between the current performance and the ultimate shape, large advances will continue and so will rule exploits. Wind tunnels have gotten so advanced and expensive to build and operate, I think they’re in a higher point on the development curve than CFD is. With large computing power getting so affordable, I think that will continue accelerating but also spread to all levels of motorsport.

SH: Awesome, thank you very much for taking the time to answer these questions and share your knowledge and experience with us all!